KR102559235B1 - Conductive metal coated plate type Nickel powder production method for semiconductor chip performance test socket - Google Patents

Abstract

The present invention relates to a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for manufacturing a semiconductor test socket. The semiconductor test socket is a method of processing nickel powder into plate-shaped powder in a short time through high-energy milling. Plate-shaped powder has the effect of significantly reducing electrical resistance by inducing contact between powders into surface contact, so it has the effect of being used as a key material for developing high-frequency test socket parts.

Description

Conductive metal coated plate type nickel powder production method for semiconductor chip performance test socket}

The present invention relates to a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket used for performance testing of a semiconductor chip, and to nickel powder thus produced.

Semiconductor test sockets are classified into Pogo type and Rubber type. The test socket is a component that connects the bump ball (aka solder ball) at the bottom of the semiconductor chip and the surface electrode of the test board. In the actual test process, when the test socket is pressed with a low pressure after being assembled in the order of semiconductor chip-test socket-test board, the test socket in the form of a sheet is elastically pressed and deformed to become conductive, which causes current to flow. These test sockets include a pogo type and a rubber type.

Pogo type is an elastic part in the form of a metal spring (IEEE Trans. Device Mater. Rel., vol. 14, no. 1, pp. 580-582, Mar. 2014), and rubber type is a composite material part in which silicon rubber and metal powder (preferably nickel powder) coated with conductive metal are mixed (IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, VOL. 8, No. 12, DECEMBER, pp. 2152-2162, 2018).

A conventional nickel powder used in a rubber-type test socket has a spherical shape with a size of several tens of micrometers, and a surface of the powder is coated with silver or gold, which is a metal having excellent conductivity. For reference, the rubber type test socket manufacturing process is as follows.

First, prepare a liquid silicone rubber. Next, it is mixed with metal silver or gold-coated nickel powder and uniformly dispersed through a mixer. The prepared liquid silicone rubber in which the nickel powder is dispersed is injected into the bottom (lower part) of the socket mold, and the mold is fastened. It is charged into a magnetic molding machine and a magnetic field is applied in the vertical direction of the mold while applying temperature. In this process, the nickel powders are closely rearranged in the direction of the magnetic field, and channels having various pitches are formed according to the structure of the mold. Then, as time passes, when the silicone rubber is cured, the part is completed. The main technique here is the contact frequency of the nickel powder forming the channels. Typically, the contact frequency is usually between 30,000 and 50,000 times. Accordingly, the electrical resistance changes greatly, and the performance of the test socket component is limited. In addition, for a high-frequency semiconductor of 70 GHz or higher, the contact area of the nickel powders of the test socket should be increased to lower the electrical resistance.

Nickel powder used in a conventional rubber-type test socket uses spherical powder, which forms point contact in the channel. In order to increase the point contact area, a technique of attaching small protruding nickel powder to the surface of large nickel powder has also been reported. This type of powder material has a limitation in that it is difficult to increase the contact area due to the limitation of point contact along with the problem of difficult manufacturing process and very high price. Japanese Patent Publication JP2000149665A (anisotropic conductive sheet, anisotropic conductive layered product and manufacture of the product), which is a similar known technology, proposes a method for designing a silicon rubber-type test socket with various axial ratios, but the shape control technology of the nickel powder material used is not well known. In addition, the known technology, Patent Registration 10-1748184 (Application No. 10-2016-0012957) (Name of Invention: Inspection A method for manufacturing conductive particles of a socket and a test socket) combines a body and sacrificial powder, and then vaporizes and removes the sacrificial powder to increase electrical contact. This method is complicated, and has a problem in that it is difficult to manufacture powder of a certain shape.

As a solution to this, the present invention has been devised to reduce the electrical resistance of the test socket by changing the contact method between the nickel powders from a point contact to a surface contact by converting nickel powder into a plate shape (disc). The core of this technology is to change the spherical nickel powder material into a plate shape. Therefore, the present invention relates to a method for producing a plate-shaped powder coated with silver or gold, which is a conductive metal, on the surface, and will be described in detail below.

An object of the present invention proposed to solve the problems of the prior art described above is to provide a method for manufacturing a conductive metal film-coated plate-shaped nickel powder material for a semiconductor test socket in which a conductive metal film-coated nickel powder material for a semiconductor test socket is rearranged in parallel with a magnetic field direction by using a horizontal high-energy milling device to transform the shape into a plate-type nickel powder material that induces contact between powders into surface contact.

Another object of the present invention is to provide a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket, in which the coated conductive metal film is not separated.

In Example 1 of the present invention of a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for semiconductor test sockets for achieving the above object, the step of preparing nickel powder, the mixing step of mixing the nickel powder and the milling balls at a predetermined ratio, a minimum of 5 to a maximum of 30: 1 in weight ratio, and rearranging the nickel powder parallel to the direction of the magnetic field to change the contact between the powders to surface contact. and performing high-energy milling in a head-on collision mode for a predetermined time period and coating the plate-shaped nickel powder with a conductive metal film.

In Example 2 of the present invention, preparing nickel powder, coating a conductive metal film on the nickel powder, mixing the nickel powder and the milling balls at a predetermined ratio, minimum 5 to maximum 30: 1 weight ratio, adding a lubricant so that the metal film does not separate in high-energy milling, rearranging the nickel powder parallel to the direction of the magnetic field to change the contact between the powders to surface contact. and performing high-energy milling for a predetermined time in a head-on collision mode by charging the milling device.

In a preferred embodiment of the present invention, in the step of preparing the nickel powder, the nickel powder has a spherical shape.

In a preferred embodiment of the present invention, the conductive metal layer is a silver or gold layer.

In a preferred embodiment of the present invention, the lubricant includes a solid lubricant or a liquid lubricant.

Unlike the conventional coated spherical powder, the present invention is characterized in that, first, from commercial nickel powder coated with silver (Ag) or gold (Au), powder of various shapes (preferably, spherical) is changed into plate-like powder in a short time through high-energy mechanical milling process parameters and milling condition changes, and at the same time, the surface conductive coating layer is not separated.

The powder prepared in this way is mixed with liquid silicon and molded through a magnetic molding machine, and the plate-shaped nickel powders are rearranged parallel to the direction of the magnetic field to induce surface contact between the powders, thereby greatly reducing electrical resistance. This effect has an effect that can be used as a core material in developing high frequency test socket parts.

1 is a flowchart of main steps according to Example 1 of a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for manufacturing a semiconductor test socket to implement the present invention.
2 is a flowchart of main steps according to Embodiment 2;
Fig. 3 shows the mechanism by which spherical nickel powder changes to plate-like nickel powder in the head-on impact mode of the high-energy milling step.
FIG. 4 is an electron microscope image of a powder prepared by high-energy milling of silver or gold-coated protruding nickel powder according to Example 2. FIG.
5 is a cross-sectional structure diagram of the plate-shaped powder prepared according to Example 1 used in a rubber socket and aligned.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, it should be understood that this is not intended to limit the present invention to specific embodiments, and includes all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In addition, the ball used here means a milling ball, the powder means nickel powder, and coating and plating should be understood as the same meaning.

The present invention will be described in more detail with reference to the accompanying FIGS. 1 to 5 . 1 is a flowchart of a method for manufacturing a plate-shaped nickel powder material coated with a conductive metal film for manufacturing a semiconductor test socket in order to implement the present invention.

Example 1

Example 1 of the present invention is a step of preparing nickel powder, a mixing step of mixing the nickel powder and milling balls at a predetermined ratio, a minimum of 5 to a maximum of 30: 1 weight ratio, a step of rearranging the nickel powder parallel to a magnetic field direction to induce surface contact between powders, charging the mixed nickel powder and the milling balls into a horizontal high-energy milling device to perform high-energy milling in a frontal collision mode for a predetermined time, and coating a conductive metal film on the plate-shaped nickel powder Include steps.

In the step of preparing the nickel powder, the size of the nickel powder varies, but is usually 10 to 50 micrometers. Most preferably, a powder having a size of around 20 micrometers is preferred. The thickness of the silver (Ag) or gold (Au) coating film is usually several micrometers, preferably around 0.5 to 1 micrometer.

The form of the powder may be single or spherical of various sizes, or a large powder (nodular type powder) to which small spherical powders are attached. However, even non-spherical powder is applicable. Most preferably, a spherical powder having a constant size is used.

In the mixing step of mixing the nickel powder and the milling balls at a predetermined ratio, a minimum of 5 to a maximum of 30: 1 by weight, the predetermined ratio of the nickel powder and the milling balls is determined according to the size of the nickel powder and the size of the milling balls. It is difficult to set a predetermined ratio. However, at a minimum of 5:1 or less, the probability of collision between the powder and the milling ball is low, resulting in a decrease in efficiency. At a maximum of 30:1 or more, contaminants may be mixed due to ball-to-ball collision, and the milling ball is made of stainless steel as a metal type and zirconia or silicon nitride as a metal oxide type.

In the step of high-energy milling by loading the mixed nickel powder and milling balls into a high-energy milling device and rotating the impeller of the milling device at a rotational speed at which the milling balls can collide head-on, that is, by setting the head-on collision mode, the high-energy milling device includes mechanical alloying for milling two or more kinds of mixed raw material powder and mechanical milling for simply grinding pure metal, intermetallic compound, or pre-alloyed powder, and usually uses a vertical high-energy milling device with a vertical axis of rotation in most cases. In milling in which powder and milling balls (milling (grinding) media) are mixed and rotated, at the normal rotational speed of the impeller, the collision between the balls acts as a slip or shearing motion mode. In the case of high-speed rotation, that is, when the number of revolutions (rpm) exceeds a critical value, the balls and powder tend to be separated from each other due to the difference in gravity. In order to change the shape of powder of various shapes (preferably spherical) into plate-shaped powder, the milling balls must collide with strong force in both directions so that the powder of various shapes located between the milling balls can be changed into plate-shaped powder. Therefore, it is unimaginable to change the shape of powder of various shapes into plate-shaped powder in a conventional vertical high-energy milling device.

Therefore, when the impeller is rotated at high speed by mixing powder and milling balls (milling (grinding) media) using a horizontal high-energy milling device with a horizontal axis of rotation instead of a vertical high-energy milling device, the number of revolutions (rpm) exceeds the critical value. The collision between the balls changes from the sliding or shear motion mode to the head-on collision mode. Therefore, in the milling step, the impeller (rotor) of the high-energy milling device must be rotated at a rotational speed that changes from the shear motion mode to the frontal impact mode. The critical rotational speed of the impeller of the high-energy milling machine is inversely proportional to the diameter of the impeller. Therefore, the number of revolutions of the impeller should not be limited to a specific value. Here, the nickel powder is plastically deformed by the vertical compressive stress of the ball as shown in FIG. 3 in the head-on collision mode to produce plate-shaped nickel powder. If the rotational speed of the impeller is too high in the milling step, impurities may be generated as described above. The milling time may be selected according to the number of revolutions of the impeller and the mixing ratio of the milling ball and the nickel powder, but is usually 10 to 30 minutes appropriate (see Table 1 below). and coating a conductive metal film on the plate-shaped nickel powder prepared in the milling step. The conductive metal film is a silver or gold coated conductive film. A conductive metal film is an essential component of the test socket.

The nickel powder prepared in this way can be classified according to size and used as a nickel powder material for a pressurized conductive rubber-type test socket.

Example 2

Example 2 includes a step of coating a conductive metal film thereon after the step of preparing the nickel powder of Example 1. Preferably nickel powder or coated with gold. In particular, in the case of spherical nickel powder, coating the sphere is easier and has a better coating effect than coating the plate-shaped nickel powder. This is because the spherical shape can make the coating layer more uniform than the plate shape.

Next, a step of adding a lubricant is further included. This is because the coated spherical nickel powder changes into a plate-like shape and has edges, and thus the coated conductive metal film can be separated from the nickel powder by frictional force when the nickel powder collides with the milling balls. For example, when the mixing ratio of the milling balls is too high compared to that of the nickel powder, the rotation speed of the impeller is too high, or the predetermined milling time is exceeded, the coating layer may be separated from the powder due to the friction force when the powder and the milling balls collide. In particular, the liquid lubricant is effective in maintaining the coating layer by effectively reducing surface friction even with the addition of a small amount. Therefore, the present invention includes adding a lubricant so that the coated conductive metal film is not separated from the nickel powder.

The amount of lubricant can be used from a minimum of 1wt% to a maximum of 15wt%, and it is preferable to maintain about 5wt%. Below 1wt%, there is no lubrication effect, and above 15wt%, the viscosity of the mixture of powder and lubricant increases and normal milling is not performed. Please refer to the manufacturing conditions and results of the coated nickel powder produced by high energy milling in Table 1 below. Table 1 shows the shape of nickel powder prepared according to the ratio of spherical nickel powder to milling balls, milling time, and amount of lubricant, and the state of maintaining the conductive silver or gold coating film on the surface. As can be seen here, when the ratio of the spherical nickel powder to the milling balls is 1:15 to 30, the milling time is 20 to 30 minutes, and the amount of lubricant is 5 to 10%, the conductive coated silver or gold film is maintained while maintaining the plate shape. Since silver and gold, which are conductive metals, have excellent ductility, they are plastically deformed at the same time as nickel powder, and thus have the advantage of stably maintaining the shape of the coating film.

sample number manufacturing conditions milled powder state Milling Ball: Powder Ratio
(wt% ratio) milling time
(minute) slush
(%) coating state powder shape One 5:1 60 One Maintain coating film spherical/plate-shaped 2 15:1 30 5 Maintain coating film plate 3 30:1 20 10 Maintain coating film plate 4 30:1 10 15 Maintain coating film spherical/plate-shaped 5 40:1 5 20 Separation of coating film rectangle

Fig. 3 shows the mechanism by which spherical nickel powder changes to plate-like nickel powder in the head-on impact mode of the high-energy milling step. Referring to FIG. 3, in the high-energy milling step, spherical nickel powder 2 having a metal film 3 coated with silver or gold is plate-shaped (disk-shaped) by strong vertical pressure of the milling ball 1. It is changed into nickel powder 2'.

The plate-shaped nickel powder coated with the conductive metal film prepared in the above-described embodiments is mixed with liquid silicon and charged into a molding mold including a magnetic molding machine, and a strong magnetic field is applied to the mold in a vertical direction through the magnetic molding machine. At the same time, heat treatment and hardening are performed. When a strong magnetic field is applied perpendicularly to the mold in the magnetic forming machine installed in the mold, the nickel powders are rearranged parallel to the direction of the magnetic field. The plate-like nickel powder is arranged in parallel with the magnetic field direction compared to the spherical powder because the magnetic anisotropy is small. 5 is a cross-sectional structure of a rubber test socket using plate-shaped powder manufactured according to embodiments of the present invention. Referring to this, it can be clearly seen that the powders inside the silicon rubber are well-aligned in the direction of the magnetic field and form surface contact by magnetic molding. In the test process, since the plate-shaped nickel powder is arranged in parallel with respect to the direction of the magnetic field, when pressure is applied to the test socket during the test process, it induces surface contact between the powders and has the effect of greatly reducing electrical resistance. As the electrical resistance decreases, it has the advantage of being used as a test socket component for high frequency.

A good example implemented

In a preferred embodiment of the present invention, protruding powder having an average size of about 20 micrometers was used. The nickel powder was coated with conductive silver (Ag) to a thickness of 1 micrometer or gold (Au) to a thickness of 0.5 micrometer.

The prepared powders were injected into a horizontal high-energy milling device (Zoz, model name: CM01). The rotation speed (speed) of the impeller (rotor) of the milling device is 1,000 rpm, and the head-on collision mode is maintained. The milling balls were made of zirconia, the ball-to-powder ratio (weight ratio) was 15:1, the milling container was charged with inert argon gas to prevent contamination by oxidation, and the milling time was 30 minutes.

A lubricant was used as a method for uniform milling and avoiding separation of the coating film. In this preferred embodiment, 5 wt% of ethanol was added. According to the flow chart as indicated in FIG. 2, the coated powder was made into a plate-shaped powder in the process of head-on collision with the ball.

4 is an electron microscope image of a powder prepared by high-energy milling of silver or gold-coated protruding nickel powder according to the conditions of the embodiment. The shape of the powder was plate-shaped (disk-shaped), the size was about 20 to 40 micrometers, and the thickness was 7 to 10 micrometers. It was confirmed that the test socket using the plate-shaped powder material manufactured in the above-described preferred embodiment can be used for testing high-frequency semiconductors of 100 GHz or more.

1: milling ball
2: nickel powder
3: metal film

Claims (6)

In the manufacturing method of plate-shaped nickel powder material coated with a conductive metal film for semiconductor test sockets,
preparing nickel powder;
A mixing step of mixing the nickel powder and the milling balls in a weight ratio of at least 5 to at most 30: 1;
Loading the mixed nickel powder and the milling balls into a horizontal high-energy milling device so that the nickel powder is rearranged in parallel with the direction of the magnetic field to change the contact between the powders into a plate-shaped nickel powder that induces surface contact, and high-energy milling for a predetermined time in a head-on collision mode;
A method of manufacturing a plate-like nickel powder material coated with a conductive metal film for a semiconductor test socket, comprising the step of coating the plate-like nickel powder with a conductive metal film. In the manufacturing method of plate-shaped nickel powder material coated with a conductive metal film for semiconductor test sockets,
preparing nickel powder;
coating a conductive metal film on the nickel powder;
A mixing step of mixing the nickel powder and the milling balls in a weight ratio of at least 5 to at most 30: 1;
Adding a lubricant so that the metal film does not separate in high energy milling;
Loading the mixed nickel powder and the milling balls into a horizontal high-energy milling device so that the nickel powder is rearranged in parallel with the direction of the magnetic field to change the contact between the powders to surface contact, and performing high-energy milling for a predetermined time in a frontal impact mode. According to claim 1 or 2,
In the step of preparing the nickel powder, the nickel powder has a spherical shape, a method of manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket. According to claim 1 or 2,
The method of manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket, wherein the conductive metal film is a silver or gold film. According to claim 2,
The method of manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket, wherein the lubricant includes a solid lubricant or a liquid lubricant. A plate-shaped nickel powder coated with a conductive metal film for a semiconductor test socket manufactured by the method of manufacturing a plate-shaped nickel powder material coated with a conductive metal film for a semiconductor test socket according to claim 1 or 2.